Upper Rhine Graben

in western Germany.

Formation

to the north of the Alps [Sengor, A.M.C. 1976. Collision of irregular continental margins: Implications for foreland deformation of Alpine-type orogens. Geology, 4, 779-782.] . The result was substantial crustal thinning, forming a major extensional graben and causing isolated volcanic activity. The stretch factor is estimated to be ~2.

Rift Flank Uplift

zones.

Volcanic Activity

The extension induced by the formation of the Alps was sufficient enough to thin the crust and provide suitable dilational conduits for magmatic and volcanic activity to occur. This resulted in the emplacement of mafic dykes which follow the general structural trend of the extensional faults. In addition, isolated volcanoes such as the Kaiserstuhl were formed.

The Kaiserstuhl Volcano

The Kaiserstuhl (literally "Emperor's Chair") is a cluster of volcanic hills to the northwest of Freiburg, within the Rhine Graben. The highest point of this small, isolated volcanic centre is the Totenkopf (557 metres). Volcanic activity was most prevalent in the Miocene epoch, some 15 million years ago [Allen, P.A. & Allen, J.R. 2005. Basin Analysis: Principles and Applications (Second Edition). Blackwell Publishing.] . Today, the Kaiserstuhl volcano is extinct.

eismic Activity

In 1356, the Basel earthquake occurred in the Rhine Graben. It was perhaps the most destructive earthquake ever to have occurred in northwest Europe, destroying the city of Basel and flattening buildings as far as 200 km away. However, it remains disputed whether the fault that ruptured to cause this earthquake was indeed part of the Rhine Graben extensional system, or simply one of the many thrust faults that make up the Alps to the south.

References